1. Field of the Invention
This invention relates to heat exchangers, and is particularly concerned with fiber reinforced composite leading edge heat exchangers for aerospace application.
2. Description of the Prior Art
Heat exchangers used in high heat flux applications such as in the leading edges of hypersonic cruise vehicles, combustion chamber walls of rocket engines, and engine walls of combined-cycle engines require materials that have high thermal conductivity, good strength at cryogenic and elevated temperatures, and excellent resistance to thermal mechanical fatigue. These heat exchangers are designed to be thermally efficient yet meet the structural load requirements. As a result, the heat exchanger configurations for these aerothermal applications often involves an array of intricate parallel subsurface cooling passages that have a high pressure fluid flowing within them. The wall thicknesses of the face sheet and lands are typically less than 0.05 inch and are held to very tight tolerances. FIG. 1 illustrates the intricate cooling fluid passages 10 in a prior art heat exchanger section 12 having walls 14 and lands 16 between passages 10.
British Patent No. 1,048,872 to Junkers discloses a method of cooling the outer skin of aircraft in which fuel as coolant is fed before combustion through passages forming the leading edge of the aircraft wing, for cooling portions of the outer skin.
U.S. Pat. No. 4,786,015 to Niggemann discloses a cooling unit for dissipating aerodynamic heating in hypersonic aircraft formed of a load bearing structure for the leading edge of an airfoil. The load bearing structure is of hollow construction defining a fluid path at one end and a fluid outlet at the other end, the fluid path comprising a tortuous path through the load bearing structure. The load bearing structure of this patent is comprised of hollow metal tubes helically wound in side-by-side relation, into an elongated tubular configuration.